Wednesday, Jul. 17, 2019

The Army Fires Dynamite Guns on Marin County

By Robert L. Harrison · September 29, 2017

 <span>&copy; National Archives </span>

 <span>&copy; Robert L. Harrison </span>

From the time when California was admitted as a State, September 9, 1850, the U. S. Army has made the protection of San Francisco Bay a high priority.   Several fortifications were constructed in the mid-19th century to ensure no enemy would pass through the Golden Gate.  Coastal defenses were built at Alcatraz Island, Fort Mason and Fort Point.

Work on Fort Point, located at the south edge of the Golden Gate, was begun in 1853. Throughout the Civil War (1861-1865) the artillerymen at the Fort stood guard but never fired a shot in anger. The captain of the Confederate raider CSS Shenandoah considered an attack on San Francisco but decided it would be impractical.  In any event he learned that the war had ended before the raid could be carried out.  Fort Point today is one of the finest examples of Civil War era military architecture anywhere in the country.

As military technology progressed the Army adopted various forms of the most modern weaponry.  In the 1880’s a class of artillery was developed known as the dynamite gun. This gun used compressed air to propel a projectile filled with high explosive dynamite or nitroglycerin.  There was a need for such a weapon because early high explosives were unstable, often uncontrollably detonated by the violent action of a standard gun powder propellant.  The compressed air gun more gradually accelerated the projectile through the length of the weapon’s barrel.  The military spent over a million dollars (over $30 million in 2017 dollars) perfecting the pneumatic dynamite gun.

Because the Army placed high priority on guarding the Golden Gate, the new technology was installed at the Presidio of San Francisco.  Battery Dynamite, located on the bluff overlooking the entrance to the harbor -about one-half mile south of Fort Point- consisted of three imposing 15-inch guns with unusually long 52-foot barrels.  The battery included the extensive below ground concrete cellars that housed a powerhouse, steam generators and air-compressors needed to fire the 43-ton weapons.  The air-compressors produced a pressure of up to 2,000 pounds per square inch or about 176,000 pounds of thrust on the base of the shell.

The new weapons were tested at the Presidio in December 1895.  The test firings appeared to be quite successful.  The official tests included shots fired at old hulks towed out to sea.  At a range of nearly three miles four shots devastated the hulks, all landing within an area of about 200 feet square.

To demonstrate the impact these shots could have on land targets, the manufacturer of the weapons recommended firing across the Golden Gate into Marin County.  The guns were aimed at a location between Point Bonita and Point Diablo in the Marin Headlands, a distance of about two miles across the Golden Gate.  With the exception of the lighthouse at Point Bonita, in 1895 this was a remote and unpopulated area of Marin with neither military nor civilian development. The military officer in charge approved the shelling of Marin.

The Army fired one of the smaller projectiles on Marin - just 100 pounds of nitroglycerine gelatin.  Nevertheless, even this smaller shell produced a hole over six-feet deep and 30 feet-in diameter in the Headland’s rocky bluff.

To demonstrate the weapons accuracy, a second gun was aimed at the point where the first shell landed.  The second shell struck the bluff only a few feet away from the first, further exacerbating the damage to the headland. 

The Army officers present declared the test firing eminently satisfactory.  The shots destroyed the naval targets, raised geysers of sea water and decimated dozens of fish. The shots on land inflicted significant upheaval to the bluffs of the Marin Headlands.

While the tests in 1895 appeared successful, the installation of the dynamite gun was short-lived.  By the early 1900s the dynamite gun was rendered obsolete by its shear mechanical complexity, as well as the availability of stable high explosives and the ever increasing range of conventional artillery.  

In 1904 the War Department declared the gun superseded and determined to dismantle the dynamite batteries as soon as possible.  In the summer of 1904 the guns at the Presidio were offered for sale to the highest bidder.  It was reported that the new owner of the guns attempted, without success, to re-sell them to Russia with a plan to ship them to Vladivostok. 

Today the concrete fortifications at the Presidio’s Battery Dynamite are still in place but have been extensively overgrown.  The remarkable pneumatic guns of Battery Dynamite were sold for scrap.  

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